Wednesday, September 25, 2013

New paper finds Ireland climate controlled by natural ocean oscillations and Sun over past 5000 years

A new paper published in Palaeogeography, Palaeoclimatology, Palaeoecology reconstructs the climate of Ireland during the past 5000 years and finds "Some terrestrial palaeo-climatic changes in Ireland appear to coincide with changes in the North Atlantic [Oscillation or NAO] and solar activity." The authors show reconstructed solar activity has increased over the past 500 years to some of the highest levels of the past 5000 years, and correlation with some warming periods. Reconstructed CO2 levels, however, do not show any apparent correlation with temperature or precipitation during any portion of the past 5000 years.

Abstract

We examine mid- to late Holocene centennial-scale climate variability in Ireland using proxy data from peatlands, lakes and a speleothem. A high degree of between-record variability is apparent in the proxy data and significant chronological uncertainties are present. However, tephra layers provide a robust tool for correlation and improve the chronological precision of the records. Although we can find no statistically significant coherence in the dataset as a whole, a selection of high-quality peatland water table reconstructions co-vary more than would be expected by chance alone. A locally weighted regression model with bootstrapping can be used to construct a ‘best-estimate’ palaeoclimatic reconstruction from these datasets. Visual comparison and cross-wavelet analysis of peatland water table compilations from Ireland and Northern Britain shows that there are some periods of coherence between these records. Some terrestrial palaeoclimatic changes in Ireland appear to coincide with changes in the North Atlantic thermohaline circulation and solar activity. However, these relationships are inconsistent and may be obscured by chronological uncertainties. We conclude by suggesting an agenda for future Holocene climate research in Ireland.